Mass spectrometry is an analytical technique that can be used to identify the chemical composition of a sample based on the mass-to-charge (m/z) ratio of charged particles. A sample comprises charged particles or undergoes ionization to form charged particles. The ratio of charge to mass of the particles is typically determined by passing them through electric and magnetic fields in a mass spectrometer.
Mass spectrometry has both qualitative and quantitative uses, such as identifying unknown compounds, determining the isotopic composition of elements in a compound, determining the structure of a compound by observing its fragmentation, quantifying the amount of a compound in a sample, studying the fundamentals of gas phase ion chemistry (the chemistry of ions and neutrals in a vacuum), and determining other physical, chemical, or biological properties of compounds.
FIG. 1 shows an example of ion-optics 100 of a typical triple quadrupole mass spectrometer system. The ion-optics 100 of a mass spectrometer generally has three main modules: an ion source 101, which transforms the molecules in a sample into ions 113; a mass analyzer 103, which sorts the ions 113 by their mass-to-charge ratios by applying electric and magnetic fields; and a detector 105, which measures the value of some indicator quantity and thus provides data for calculating the abundances of each ion present.
In the case of a triple quadrupole mass spectrometer, the mass analyzer 103 has a series of three quadrupoles. A first quadrupole 107 and a third quadrupole 111 act as mass filters. A middle quadrupole 109 is included in a collision cell. This collision cell uses gas to induce fragmentation (collision induced dissociation) of selected precursor ions from the first quadrupole 107. Subsequent fragments are passed through to the third quadrupole 111 where they may be filtered or scanned fully.
The use of the three quadrupoles allows for the study of fragments (product ions), which is very helpful in structural elucidation. For example, the first quadrupole 107 may be set to “filter” for an ion of a known mass, which is fragmented in the middle quadrupole 109. The third quadrupole 111 can then be set to scan the entire m/z range, giving information on the sizes of the fragments made. Thus, the structure of the original ion can be deduced.
Sometimes components of the ion-optics 100 can become dirty, malfunction, or might require regular periodic maintenance, and therefore must be accessed or removed by a user. However, it is inconvenient to access or remove ion-optics components from prior-art mass spectrometers. For example, certain mass spectrometers (e.g. U.S. Pat. No. 6,069,355) have separate vacuum chambers and standard vacuum connections, making it very difficult and time consuming to access or remove components internal to the vacuum chambers. Additionally, components of the ion-optics 100 must be precisely positioned and aligned with each other when reassembled inside the mass spectrometer.
In the prior-art, internal components are often aligned using alignment systems, such as rails, to which all of the internal components are mounted. Other alignment systems make use of a precision machined chamber into which the internal components are inserted. The liquid chromatography triple quadrupole mass spectrometer instrument (LC/QQQ) by AGILENT TECHNOLOGIES, INC, is an example of a mass spectrometer making use of such alignment techniques. However, in these prior-art alignment systems, parts of the alignment systems can be far apart compared to the components that are to be aligned. This can lead to problems with tolerance stack-up and difficult-to-achieve machining tolerance requirements, causing such systems to be more complex and expensive to fabricate. Here tolerance stack-up, also known as tolerance stack or tolerance stackup, is a term used to describe the variation that occurs as a result of the accumulation of specified dimensions and tolerances.
It would be desirable to provide fast and convenient access to mass spectrometer components while at the same time allowing for the components to be reassembled with precise positioning and alignment.